Siemens SIMATIC S5 Manual page 251

(1) The maximum runtime is required when a job is being carried out,
e.g. AS1 – change setpoint controller 1 – and the error messages must also be
read. This would be the case in each fifth S5 cycle if errors have occurred.
The total processing time consists of the time to execute the command and the
time required for "read errors".
Example with S5-135U, CPU 922:
AS = 6.9 ms
AS = 6.9 ms + 6.5 ms = 13.4 ms
The commands grouped together above have similar execution times. The time shown in the table
is the maximum time.
The commands PA and AE require that the function block FB 162 is called twice (two S5 cycles).
The others require only one FB 162 call.
IP244
C79000–B8576–C861–02
Application of the Function Block
without "read errors",
with "read errors".
5–47